The present invention concerns a fluorescent film formed on the panel of the cathode ray tube of a color television receiver, and more particularly a process for treating the surface of a fluorescent material forming the fluorescent film.
Generally, the fluorescent film comprises a plurality of stripes or dots, which are formed by applying a mixture of a fluorescent material and a slurry of polyvinyl alcohol (PVA) and ammonium dichromate (ADC) to the panel, which is then dried, exposed to light and washed.
In this case, the stripes or dots should strongly adhere to the panel, avoid color mixing, and form a uniform and dense fluorescent film, which significantly depends on the surface treatment of the fluorescent material deposited on the panel.
Conventionally, a process for treating the surface of the fluorescent material comprises the steps of adding water glass (K.sub.2 O.SiO.sub.2) to a dispersion of fluorescent material, and then further adding salt such as zinc, aluminium, barium, etc. thereto, so as to precipitate a colloidal phase of a metal silicate adhering to the surface of the fluorescent material.
Although such a conventional process produces clearly formed stripes or dots of fluorescent material without color mixing, there occurs a problem that the adhering force of the fluorescent material to the panel of a cathode ray tube is weak, and the obtained fluorescent film is not dense.
Moreover, the fluorescent film deposited on the panel of the cathode ray tube of a color television receiver comprises three kinds of fluorescent material respectively coloring red, blue and green. Hence, if the adhering force of the fluorescent material to the panel is weak, the stripes or dots tend to separate from the panel, thus deteriorating the quality of the cathode ray tube.